Typically, a marine steering system includes a steering or helm pump attached to a steering wheel for directing fluid to opposite ends of an actuator cylinder which, in turn, actuates the rudder to effect steering of a boat. The hydraulic system may be a closed circuit where the flow path of oil or fluid is uninterrupted. The hydraulic fluid flow is in a continuous, uninterrupted path from the pump to the actuator and directly back to the pump. When such a system is initially filled with oil, it is difficult to remove all of the air trapped in the lines, pumps and actuator. This is due to the uninterrupted flow path where there is no escape for the trapped air. In an open circuit oil system, the oil returns to a reservoir which is, in turn, connected to the pump inlet. Unlike the open circuit, closed circuits must be blead by some other technique.
Prior art actuators included bleeder fittings wherein oil is upmpted out through the bleeder fitting in the actuator or hydraulic cylinder to flush out oil with the trapped air while fresh oil is applied to the pump. The U.S. Pat. No. 3,576,192 to Wood, issued Apr. 27, 1971 discloses an air bleeding system including a valve added to a circuit to bypass all return flow to a reservoir tank so that air is separated in a manner similar to an open circuit system. The U.S. Pat. No. 4,449,470 to Rump, issued May 22, 1984 and assigned to the assigness of the instant invnetion discloses a reservoir and bypass to a tank valve which are mounted remotely from the pump and pressurized to produce a remotely filled and bleed system.
All three of the aforementioned air bleeding systems have drawbacks when utilized in a marine steering assembly. The method wherein the oil is pumped out through a bleeder fitting requires two people to bleed the system. One person is required to turn the helm and the other to control the oil flow from the bleed fitting. This method also involves catching the oil pumped out of the system, through the bleeder fittings, which could be a slopper operation. This method is also not as efficient or as fast as the two other methods which automatically remove air. The second and third previously mentioned methods, however, add components to the hydraulic circuit which inrease its complexity and cost. The more complex the circuit is, the more reliability is reduced. Also, connecting additional systems such as auto piolots becomes more difficult. Pressurized systems such as disclosed in the Rump patent required the pressure to be maintained continuously to allow the steering system to function. This type of system is, therefore, much more sensitive to leaks than nonpressurized systems. It requires an additional pump to create the air pressure in the reservoir.
Accordingly, the instant invention produces a bleeding system that does not require additional valving as a permanent part of the circuit. It allows bleeding of the system by one person and does not require a permanently pressurized system. The system can be easily attached to the circuit and, once attached, automatically fills and bleeds the entire system. This does not require pumping oil out of the circuit into open containers.